Mazda CX-3 Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
So yesterday I had the engine light pop up on my dashboard. The Mazda warning guidance just says "engine system malfunction. Have the vehicle checked by a dealer immediately". Mine is a 2017 CX3 Touring.

I've made an appt with the Mazda dealer tommorow, but I went to Auto Zone to use their OBD2 reader just to see what it says. It gave me a code P0421.

A little googling and I think the suspect is the O2 sensor. Yesterday I was doing a little light off-roading to get to a trailhead for some hiking in the mountains. I have driven on this trail several times with no issues...there was a spot where I bottomed out for a second but I was able to backup and navigate around the sketchy section.
Anyway, my guess is the O2 sensor got jarred loose. From what I can tell it's located under the vehicle near the catalytic converter.

The car runs and idles fine otherwise. Any thoughts on my theory?
 

·
Registered
Joined
·
498 Posts
This spiked my curiosity so I looked around and probably like you have found it comes down to 3 things, o2 sensor/cat/sensor wiring and apparently at other times spark plugs. Depending on whether you get charged an arm and a leg at the dealer I would first try to look at the sensor and harnesses. Also might want to look into using a bottle of cataclean just for peace of mind(although I doubt a dirty cat is applicable to this car so soon). Its basically a voodoo fluid and usually applies to older cars which arent passing emissions due to dirty cat/02 sensor and this somehow helps clean it out. But given your previous experience the other day it seems to be most likely related to the sensor wiring, if anything you might have caused an exhaust leak depending how harsh you bottomed out which might also throw the code based on my internet broscience research.

Given how annoying o2 sensors are to take off from experience, Im hesitant to believe the sensor itself moved but thats just speculation. Follow the wiring up the car and see if anything looks off and tug at wiring at the ends they connect to things 'safely' ofcourse.

Or just let the dealer do the work if you are set on that route or repair. No use wasting time and stressing yourself out if its gonna be fixed by them anyways.

Best of luck, let us know how it turns out.
 
1 - 3 of 3 Posts
Top